Color correction in multilayer



June 1l, 1946. L'EROY M. BEARING y COLOR CORRECTION IN- MULTILAYER FILM original Filed A51-i1 s, 1940 2 sheets-sheet 1 F/cs.

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NAVE LENGTH .5 RQYMDEA/Q/NG INVENTOR ATTORNEYS June r11, 1946 LE ROY M. BEARINGl `R12 22,764 y f-JOLOR CORRECTION IN MULJIILA'X'ERl FILM Original Filed April 6, 1940 2 Sheets-Sheet 2 8L UE RED Exposl/RE AND /vEsA T/VE DEVELOPMENT JTEP CORRECT/N6 EXPOSURE FOR BLUE- JENS/ 7'/ VE LAYER AND NEGATIVE oEvEwpME/YT. /3

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Le Roy M. Bearing, Washington, C., assigner to Eastman Kodak Company, Rochester, N. Y., -a corporation of New Jersey Original No. 2,307,996, dated January 12, 1943, Serial No. 328,311, April 6, 1940. Application for reissue September 12, 1944, Serial. No.y

3 Claims.

This invention relates to color correction and particularly to the method for securing color 'correction in printing multi-layer color film.

It is well known that duplicates made from multi-color photographic originals have considerlably desaturated blues and greens.

This is due to the fact that some of the subtractive color dyes used in lthe lm especially the blue-green and magenta dyes do not transmit blue light as thoroughly as they should. 'I'he blue-green dye may absorb as much as 20% of the blue light and the` magenta dye as much as 15% of lthe blue light although both of these should be completely transparent to blue. The results of this absorption is that all of the blues on the original transparency will, during the duplicating printing exposure, prevent complete exposure of the bluesensitive layer in the duplicating illm or paper. When this iilm Y or paper is reversed during processing, it may, therefore, contain nearly 40% oi' yellow dye in what should be a clear blue area. As a result, skies and other parts of the scene which should appear blue frequently appear green in the duplicate.

This defect in color process is well known and has been overcome in practice by the use of various masking methods. For example, a low contrast red separation positive or such positive combined with a low contrast green separation `positive has been. used as a mask for the blue separation negative. Other separation negatives 2 f sorption is exposed through a negative silver image in at least one other layer and the exposed portion then developed to a negative before exposure and development of the film to form positive images in it. l y

In the accompanying drawings, Fig. -l is a graph illustrating typical absorption curves for the usual subtractive dyes used in color processes that is the yellow, magenta and bluegreen dyes.

, Y Fig. 2 isl a graph illustrating the sensitivity of where it should transmit. It is evident, there may be masked in a similar manner with suitable low contrast separation positives. In the case of the blue separation negative the masking effecltively removes yellow contamination in those rts of the original which contained blue-green Masking methods of this type involve :the production of separate, low contrast. separation positives and :these must be registered with the original during printing. 'Ihese are objectionable. time-consuming and expensive features of masking methods and, therefore, they have not been widely used.

It is, therefore, the principal object of the present invention to provide a method for correction of multi-layer color iilms during printing. A further object is to provide a method for correctlon of multi-layer color films'. during processl ing after an original or negative expomre. Other objects will appear from the following description of my invention.

These objects are accomplished by exposing the film after the negative exposure and development so that at least one layer which uli-.ixnately conone type of film used according to my invention. Fig. 3 is a iiow diagram illustrating the various steps in one form of the correction process constituting my invention, the steps being illustrated by means of sectional views across the film.

It. is known that the subtractive magenta and blue-green dyes'used in most subtractive photographic processes absorb light in regions which they should transmit. As shown in Fig. l which illustrates typical absorption spectra, the bluegreen; in addition to absorbing properly in the red region, also absorbs some light in the green and the blue regions. The magenta dye in addition to absorbing properly in the green region also absorbs some light in the blue region. The yellow dye is the best of the three although it does have a slight absorption in the green region fore, that the largest correction is necessary for the blue-green and magenta dyes, that is in the blue and green regions of the spectrum.

In multi-color processes in which silverhalide layers effectively sensitive tothe blue green and red regions of the spectrum are` coated lon a single support and colored images are formed in the layers by coupling, such as inthe process de-l scribed in Mannes and -Godowsky U. S. Patent 2,113,329, April 5, 1938, it is, customaryto secure a separation ofthe colors by combined sensitizing and filtering methods. Since all silver halide emulsions are sensitive to the blue region of the spectrum', a yellow iilter layer is usually inl corporated between the blue-sensitive layer and the remaining layers or a yellow filtering mate- `rial is incorporated in the blue sensitiveA layer itself. The layer which records the green rays is sensitive only to green and bluelight andthe layer which records the red rays is sensitive only to red and blue light. The' blue sensitive layer is ordinarily coated nutermost, that is, farthest from the support.

tains an image forming dye having excessive abg If a film of this type is used for printing acy cording to my invention, it is necessary to prevent the action of blue light on the green .and red sensitive emulsions whilel exposing the blue-sensitive infrared region.

A. eration negatives is desirable'I the or it might be sensitized in the infrared or in the'l extreme ultra-violet region. 'Ihis special sensitiz- \ing is necessary only if the blue-sensitive emulsion Narrow- Iband sensitizing of multi-layer duplicating material is disclosed in Mannes and Godowsky U. S.l

is to be given acorrecting exposure.

application Serial No. 307,140, ledDecember 1,

According to my invention, if the duplicate is to be corrected for the improper blue light absorption of the blue-green and magenta dyes this specially sensitized film/ must be used. After exposure and partial or complete negative development of this material, it is given a low intensity ilash exposure of the same quality as the special sensitizing of the blue sensitive emulsion. This flash exposureis made through the support if the blue-sensitive emulsion is outerrost So that the green and red silver negatives act as masks. A second negative development follows this flash exposure and this second negative development produces silver in the blue-sensitive emulsion in those regions where the blue-green and vmagenta. dyes of the original prevented complete blue exposure. Yellow contamination ofthe blues in the duplicate is to be avoided.. The iilm is thenf reversed and color` developed or treated in any other suitable manner to form positive dye images in the layers.

Multi-layer color duplicating` lms are generally given a narrow band sensitivity so that they are rather sharply sensitized in the blue, green and red regions of the spectrum. The material used in my invention would retain this narrow band sensitizing used .for the ordinary printing exposures from the original. In addition to this narrow band sensitizing the blue-sensitive emulsion also carries a narrow band sensitizing inl any of the three regions at a band to which thegre'en and red sensitive emulsions are not sensitive. This might be either in the yellow region or in the It is also necessary that the lter layer usually present'between the blue sensitive emulsion and the other emulsions, if it has not been destroyed in the negative development, transmit fairly well in the region of the narrow band masking sensitizin'g of the blue sensitive f emulsion layer,

' In addition to the blue separation' negative, it is also possible that the complementary dyes of the original are of such impurity that the green or red separation negatives also need a masking exposure. For example, the magenta or yellow dye may not transmit all ot the red 0r the blue-green dye may not transmit all of the green. The latter case is the one we found in practice.

In this case it is unnecessary to use a special sensitizing emulsion for the duplicating material. This is due to the fact that the usual narrow band sensitizing of duplicating films in the green and red sensitive layers are suiliciently well separated that they can be used forthe masking exposure as well as tor the regular printing exposure. If desired, however, a. separate narrow band sensitization for the masking exposure can be incorpogreen-sensitive emulsion maybe dashed during or after negative development, through the red separation negative record. It the green sensitive layer is in the middle and the red sensitive layer nearest the support, the film would be flashed through the support with green light to which onlythe iniddle layer is sensitive. I'his flash exposure may be made at the same time as the ilash exposure of the blue sensitive layer or subsequently. Ihe arnountof exposure should be equal to the amount 'of green light absorbed by the blue-green dye in the original as multiplied by a factor which takes into account the diierent sensitivity of the green itv , reduce the silver halide to metallic silver.

mation of a positive dye image can then be ac-.

layer after negative development compared with its initial sensitivity.v If the yellow dye of the In a similar way the red sensitive layer can be given a flash masking exposure through the blue negative and the green negative records with a light corresponding to the quality of its own narrow band red sensitization. Any of these masking exposures may be made during or after negative development of the film at a time when there is silver negative image present. It may bedesirable to make the ash exposure during development in order to secure lower contrast when a thin negative image is present.

After any or all of the masking exposures, the film is again placed in a negative developer to Forcomplished in any suitable manner. For example, the film may be color developed as described in Mannes and Godowsky U. S. Patent 2,113,329,

Lor it may be colored by bleaching, toning or resent respectively the yellow, magenta and blueregions of the spectrum. As shown by the curves, f

X, the emulsion layers i'l and I2, are also sensitive to the blue region of the spectrum but exposure of` these layers by blue light is prevented v bythe filter layer Il between layers Il and il. Emulsion layer i2 is also sensitive to the green region of the spectrum as indicated at Y and emulsion layer Il is ,sensitive to the red region oi the spectrum as indicated atZ. In addition to its sensitivity in the blue region as indicated at X, emulsion layer Il is also sensitive to a narrow band between the green and the red regions as indicated Aat Q. The masking exposure through the support may. therefore.`be accomplished by y -means of light in the narrow spectral region Q without affecting either ot the emulsion'layers II and I2. Any silver negative imageV in llayers II and I2 will. however, prevent exposure oi layer Il at that point during the masking exposure.

Fig. 3 isa i'low chart illustrating steps in the I corresponding lexposure of a typical multi-layer iilm in which it is assumed that correction is to be made for the inadequate blue and green transmission of the blue-green and magenta dyesv of the original.

layer iilm in sectional views but illustrates the eiiect of the negative masking images rather than the eflect of the sensitivity of the layers.

The sensitivity ofthe iilm is assumed to be similar to that shown in Fig. 2.

Asshown in Fig. 3 a support I5 of any suitable transparent material such as cellulose ester, synthetic resin or paper is coated with emulsion layers I8, I1 and I8 effectively sensitive respectively to the red, green and blue regions of the spectrum. It is to be understood that the eii'ect of blue light on emulsion layers I6 and I1 is prevented by means of a yellow filtering material, not shown.

Exposure to a color transparency or to a natural scene in the camera and negative developf ment produces in this material negative images I8, .2Il and 2i, assuming that portions of the spectrum in the red, green and blue regions are present in the exposing light. The inadequate blue and green transmission of dyes in the original produces an incomplete exposure of the blue and green sensitive layers and therefore an incomplete negative image as shown at 20 and ZI. If this nlm were exposed and developed to a positive immediately, these incompletely exposed blue and green regions would develop dye images and would produce a yellow and magenta contamination which was not present in, the original.

In order to overcome this undesirable yellow and magenta contamination, the iilm is first given a masking exposure through the support with light of the color to which the layer I8 is sensitive This chart also shows the multilow, respectively, are formed in the layers as shown in step 4.

Although my process has been described with particular reference tov duplicating or printing multi-layer color iilm onto a similar material, it is to be understood that my process may also be used for correction in a negative process that is in the development of film exposed in aI camera provided that suitably sensitized material is i used or that my process can be applied to negative positive methods and that various methods of forming the positive dye images may be used. The examples given are illustrative only and it is to be understood that my invention should be limited only by the scope of the appended claims.

I claim:

l. The method of forming a corrected image in natural colors in a multi-layer photographic material having superposed layers sensitive in order to the blue,green and red regions of the spectrum, the blue-sensitive layer having an additional sensitivity in a region to which the green sensitive and the red-sensitive layers arenot sensitive, which comprises exposing the material and' developing it to negative silver images in alll 4terial having superposedlayers sensitive respecbut not layers. I6 and4 I1, that is either to the narrow band yellow or 4the infrared rays. This exposure affects only layer I8 at the places where there is no negative image in the layers IB and I'I. In the present case the silver images I9 and 2li prevent exposure of the layer IB except at the region 22 and a silver image is therefore formed in this place on further negative development.

In order to correct for the undesirable green absorption of the blue-green dye, a further masklng exposure is given to green light through the support this exposure affecting only'the green sensitive layer I1. During this exposure the silver negative image II prevents exposure of the green 1 sensitive layer at this portion and since layer I8 is not sensitivetogreen light it is unailected. The only exposure. oi' layer I1, therefore, is at the region-2l and a negative silver image is formed at this point upon further development.

' A short exposure is made to green light, to pre- 4vent the formationI of a dense image in the portively to the blue, gren and red regions of the spectrum, the blue-sen itive layer having an'additional sensitivity in a region to which the greensensitive and red-sensitive layers are not' sensitive. which comprises exposing the material and developing it to negative silver images in all exposed layers, and then, without removing said negative silver. images, exposing, through the redsensitive layer, at least one layer of the materia1` which ultimately contains an image-forming dye having excessive absorption in the-region to which that layer is sensitive, developing said exposed layer to a negative silver image supplementing the original negative silver image formed therein. and then forming positive dye images in the layers at the places of the residual, undeveloped silver halide.

3. The method oi.' forming a corrected image in natural colors in a multi-layer photographicmaterial having superposed layers sensitive in order to the blue, green and red regions oi' the spectrum, the blue-sensitive layer having an additional sensitivity in a. region to which the. green sensitive and 'red sensitive layers are not sensi-- tive, which. comprises exposing the material to :a colored photographic velopingit izo-negative silver images in I layers. dash-exposing the blue-sensitivcrlayer through the partial negative silver" images in theA and red-sensitive layers, developing said exposed v layer to negative silver images supplementing thel original negative. silverimages formed therein.'

and thenV forming positive dye images in the layers at the places of the residual, undeveloped silver halide. 4

La noYM. BEARING. 

